Phosphorylated quaternary ammonium compounds of improved oral absorption



United States Patent 9 3,090,725 PHOSPHORYLATED QUATERNARY AMMO- NIUMCOMPOUNDS 6F EMPRQVED QRAL ABSORHUON Frederick Charles Copp, ArthurMcfiouhrey, and John Evlyn Warner Billinghurst, London, England,assignors to Burroughs Wellcome 8: Co. (USA) Inc, Tuckahoe, N.Y., acorporation of New York No Drawing. Filed Feb. 14, 1961, er. No. 853,126Claims priority, application Great Britain Feb. 29, 1960 6 Claims. (Cl.167-55) The present invention relates to pharmaceutical formulations, tothe method by which the formulations are prepared, and to pharmaceuticalcompositions containing the formulations.

A limiting factor in the pharmaceutical application of quaternaryammonium compounds which have a potent systemic pharmacological orchemotherapeutic action upon parenteral administration to man or animalsor both and Whose cations contain a hydroxyalkyl group is that thesecompounds are poorly and erratically absorbed from the gastrointestinaltract, and are therefore not particularly suitable for oraladministration. This limitation has resulted in the potent therapeuticvalue of these compounds not being fully realized in medical practice.

It has been found that pharmaceutical formulations having a high degreeof absorption upon oral administration are obtained by phosphorylationof the said quaternary ammonium compounds. It has also been found thatpharmaceutical formulations having a high degree of regular absorptionupon oral administration, and thereby giving a high degree of uniformmedication, are obtained by phosphorylation of the said quaternaryammonium compounds.

According to the present invention in one aspect, there is provided amethod of improving the absorption upon oral administration of aquaternary ammonium compound which is poorly absorbed from thegastrointestinal tract but has a potent systemic pharmacological orchemotherapeutic action upon parenteral administration and whose cationcontains one or more hydroxyalkyl groups, which method comprises thephosphorylation of the compound to its phosphate ester.

According to the present invention in another aspect, there are providedthe phosphate esters of quaternary ammonium compounds, which are poorlyabsorbed from the gastro-intestinal tract but have a potent systemicpharmacological or chemotherapeutic action upon parenteraladministration and Whose cations contain one or more hydroxyalkylgroups.

The preferred phosphate esters are those of quaternary ammoniumcompounds whose cations contain one or more Z-hydroxyethyl groups.Further, the preferred phosphate esters contain one phosphate group, butesters which contain two or more phosphate groups are also within thescope of the present invention.

It will be understood that the phosphate esters exist as internal salts.Further, it will be understood that the mono-phosphate esters containone cation equivalent and the poly-phosphate esters contain anappropriate number of cation equivalent, for example, a (ii-phosphateester contains three cation equivalents; and that each of these cationequivalents is preferably pharmaceutically and therapeuticallyacceptable, for example is a hydrogen or alkali metal atom, or anequivalent of a calcium or magnesium atom, .or an ammonia group.

As used in this specification the term potent systemic pharmacologicalor chemotherapeutic action is to 'be understood as meaning a level ofsystemic therapeutic activity which is of value in medical practice.Thus, a quaternary ammonium compound which has a potent systemicpharmacological or chemotherapeutic action 3,09%,725 Patented May 21,1963 upon parenteral administration is one which it would be valuable toadminister in medical practice. Examples of such quaternary ammoniumcompounds are those which have a systemic 'anti-adrenergic (that is,adrenergic neu rone blocking or specific sympatholytic), ganglionblocking or spasmolytic action.

(i) Anti-adrenergic compounds have a specific sympatholytic action dueto depression of the 'adrenergic nerve mechanism and not due to a directantagonism of adrenaline and its congenors; they are therefore useful inthe treatment of hypertension. Examples of quaternary ammonium compoundswhich have a systemic anti-adrenergic action are described in thecomplete specifications of British patent applications Nos. 12,354/58,18,963/58, now Patent No. 881,265, 21,117/58, 4,082/ 60 and 4,850/60,and in the provisional specification of British patent application No.22,144/ 60. Specific examples of cations of such quaternary ammoniumcompounds are:

N-benzyl-N-2=hydroXyethyl-N,N-dimethylammonium;

N-benzyl-Nethyl-N-2-hydroxyethyl-N-methylammonium;

N-benzyl N,N-di- (Z-hydroxyethyl) -N-methylammonium;

N-o-bromobenzyl N,N-di-(2-hydroxyethyl) N-methylammonium;

N-o bromobenzyl N -2-hydroxyethyl-N,N-dimethyl ammonium;

N-ochlonob enZyl-N,N-'di- Z-hyidroxyethyl) -N-methylammomum;

N-o-chlorobenzyl -N-2-hydroxyethy1 N,N dimethylammomum;

N-o-fiuorobenzyl N,N-di-(2-hydroxyethyl) -N-methylammonium;

N-o-fluorobenzyl-N-2 hydroxyethyl-N,N-dimethylammomum;

N-o-iodobenzyl N-Z-hydroxyethyl N,N-dimethylamrnomum;

N-o-methylhenzyl N,N-di-(2-hydroxethyl) N-methylammonium;

N-o-methylbenzyl N-Z-hydroxyethyl N,N-dimethylammonium;

N-o-nitrobenzyl N,N-di-(2-hydroxyethy1)-N-methylammonrum;

No-o-bromobenzyl-N-Z-hydroxyethylpyrroldinium;

N-cyclohexylmethyl N-Z-hydroXyethyI-N,N=dimethyl ammonrum;

'N-(bicyclo (2,2,1)-hept-2-yl)methyl N-2-hydroxyethyl-N,N-dimethylammonium;

N-Z-hydroxyethyl N-methyl-1,2,3',4'-tetrahydroisoquinolinium;

N-Z-hydroxyethyl-N methyl-S-bromo 1',2,3,4'-.tetrahydroisoquinolinium;

N 2-(4 benzoyl 2,6 dimethylphenoxy)ethyl N,N-di

(2-hydroxyethyl) -N-methyl ammonium;

N-2-( 4-benzoyl-2, 6 -dimethylphe}noxy)ethyl-N-Z-hydroxyethyl-N,N-dimethylammonium; and

N-2-(2-bromo-4-methoxyphenoxy)ethyl N 2hydroxyethyl-N,N-dimethylammonium.

The preferred quaternary ammonium compounds which have a systemicanti-adrenergic action contain a benzyl'ammonium cation, optionallycarrying an ortho-substituent.

(ii) Ganglion blocking compounds block transmission in the ganglia ofthe autonomic nervous system, resulting in a lowering of vasomotor toneand a consequent fall in blood pressure; they are therefore useful inthe treatment of hypertension. Specific examples of cations ofquaternary ammonium compounds which have a ganglion blocking action are:Hexamethylene-1,6-b is-(N-2hydroxyethyl-N,N-dimethylammonium) and3-hydroxypentamethylene-l ,S-bis- N-metliylpyrrolidinium) (iii)Spasmolytic compounds relieve the spasms of smooth muscles caused, forexample, by exaggerated impulses from the parasympathetic nervoussystem, and by stimulation from chemical changes in the surroundingtissues; they are therefore of therapeutic value. Specific examples ofcations of quaternary ammonium compounds which have a spasmolytic actionare: N'-(o-chlorobenzhydryl) N methyl-N-2-hydroxyethylpiperazinium and N(3-cyclohexyl-3-hydroxy-3-phenylpropyl)-N-(2-hydroxyethyl)-pyrrolidinium.

According to the present invention in a further aspect, the phosphateesters of quaternary ammonium compounds which are poorly absorbed fromthe gastro-intestinal tract but have a potent systemic pharmacologicalor chemotherapeutic action upon parenteral administration and whosecations contain one or more hydroxyalkyl groups, are prepared by thehydrolysis or hydrogenolysis of an O,G-X ,X -phosphate ester of thequaternary ammonium cation, wherein X and X are each a labile 'group,such as a phenyl, benzyl, allyl, l-alkoxyvinyl or Z-cyanoethyl group.The hydrolysis is carried out under mild conditions, and thehydrogenolysis in the presence of a catalyst such as platinum oxide orpalladium. The 'O,O-X ,X -phosphate esters are prepared byphosphorylation of the quaternary ammonium cation with a phosphorylhalide such as phosphorochloridate, or by quaternisation of a tertiaryamine containing the groups desired in the quaternary ammonium cation,other than the desired hydroxyalkyl group, with an O,O-X ,X-O-Y-phosphate, wherein X and X are as defined above and Y is an alkylgroup containing a reactive atom or group.

According to the present invention in a yet further aspect, thephosphate esters of quaternary ammonium compounds which are poorlyabsorbed from the gastrointestinal tract but have a potent systemicphmmacological or chemotherapeutic action upon parenteral administrationand whose cations contain one or more hydroxyalkyl groups, are preparedby the reaction of the quaternary ammonium compound with concentratedphosphoric acid and phosphoric pentoxide. The acid is preferably inexcess, and the reaction mixture is preferably warmed and under apartial vacuum.

The phosphate esters prepared by the above described methods ofpreparation may be converted by double decomposition, for example insolution or on an in exchange column, into esters containing difierentcation groups. This may be particularly desirable if an ester which isnot therapeutically acceptable, for example one wherein barium is thecation, is first prepared.

According to the present invention in two yet further aspects, there areprovided a pharmaceutical composition which comprises a phosphate esterof a quaternary ammonium compound which is poorly absorbed from thegastro-intestinal tract but has a potent systemic pharmacological orchemotherapeutic action upon parenteral administration and whose cationcontains one or more hydroxya'lkyl groups, and a pharmaceuticallyacceptable carrier therefor; and the method of making the pharmaceuticalcomposition by inclusion of the phosphate ester with the acceptablecarrier. The pharmaceutical composition is preferably administeredorally, but a composition which is administered parenterally also fallswithin the scope of the term pharmaceutical composition. For oraladministration, fine powders or granules of the ester may containdiluents and dispersing and surface active agents, and may be presentedin a draft in water or in a syrup; in capsules or cachets in the drystate or in a nonaqueous suspension, when a suspending agent may beincluded; in tablets, when binders and lubricants may be included; or ina suspension in water or a syrup or an ioil, or in a water/ oilemulsion, when flavouring, preserving, suspending, thickening andemulsifying agents may be included; the granules or the tablets may becoated.

'For parenteral administration, the'ester may be presented in aqueousinjection solutions which may contain anti oxidants, buffers,bacteriostats, agents which solubilise a relatively insoluble ester, andsolutes which render the ester isotonic with the blood; or in solutionsor suspensions, which are non-aqueous if the ester is affected by water;extemporaneous injection solutions may be prepared from sterile pills,granules or tablets which may contain diluents, dispersing and surfiaceactive agents, binder and lubricants; the injection solutions orsuspensions may be presented in unit dose ampoules or multi-dosecontainers. The preferred form of pharmaceutical composition is tablets.

The effective dose range of the phosphate ester to be administereddepends on a number of variable factors. Thus, it will depend on thetoxicity and the mode and frequency of administration of the particularester. In particular, however, it will depend on the activity of thequaternary ammonium compound which is poorly absorbed from thegastro-intestinal tract but has a potent systemic pharmacological orchemotherapeutic action upon parenteral administration and whose cationcontains one or more hydroxyalkyl groups, because the therapeuticactivity resides in the quaternary ammonium cation and thephosphorylation only improves the absorption of the quaternary ammoniumcompound upon oral administration.

According to the present invention in a yet further aspect, there isprovided a process for the treatment of hypertension which comprises theadministration of a phosphate ester of a quaternary ammonium compoundwhich is poorly absorbed from the gastro-intestinal tract but has apotent systemic anti-adrenergic or ganglion blocking action uponparenteral administration and whose cation contains one or morehydroxyalkyl groups.

According to the present invention in a yet further aspect, there isprovided a process for the treatment of spasms of smooth muscle whichcompries the administration of a phosphate ester of a quaternaryammonium compound which is poorly absorbed from the gastrointestinaltract but has a potent systemic spasmolytic action upon parenteraladministration and whose cation contains one or more hydroxyalkylgroups.

The invention, whose scope is in no way limited thereby but is fullydescribed herein, will now be described by reference to the followingexamples,'in which all temperatures are given in degrees Centigrade.

Example 1 N-c-chlorobenzyl-N,N-dirnethyl N 2 hydroxyethylammonium iodide(5 g.) was suspended in 90% phosphoric acid (15 g.) and heated at for 3hours under reduced pressure with an air leak to remove hydrogen iodide.Phosphorus pentoxide (4 g.) was added in small portions with cooling,and the heating then continued under reduced pressure for 2%; hours. Themixture was poured into water (50 ml.) and a hot concentrated solutionof barium hydroxide added with cooling until the mixture was justalkaline. The barium phosphate was filtered ofl? and washed. Thefiltrate was made slightly acid by 5 N-sulphuric acid and the bariumsulphate centrifuged down. The supernatant was evaporated under reducedpressure and the residue dissolved in alcohol, blacked, filtered andevaporated to dryness. The residue was crystallised from alcohol to giveN-o-chlorobenzyl- N,N-dimethyl N 2 phosphatoethylammonium betaine,melting point 221 Example 2 N-o-bromobenzyl-N,N-dimethyl N 2hydroxyethylammonium iodide was converted to N-obromobenzyl-N, N-dimethyl-N-Z-phosphatoethyl ammonium betaine, melting, point 209-210",by methods analogous to those described in Example 1 and crystallisedfrom acetonealcohol.

Example 3 N-o-methylbenzyl-N,N-dimethyl N 2 hydroxyethylammonium iodidewas converted to N-o-methylbenzyl-N,N-dimethyl-N-Z-phosphatoethylammonium betaine, melting point 209, bymethods analogous to those in Example 1 and crystallised fromacetone-alcohol.

Example 4 N o chlorobenzyl N methyl-N,N-di-(Z-hydroxyethyl)ammoniumchloride was converted to N-o-chlorobenzyl Nmethyl-N,N-di-(2-phosphatoethyl)ammonium betaine, melting point218-219", by methods analogous to those described in Example 1 andcrystallised from ethanol.

Example 5 A mixture of N-2-(4benzoyl-2,G-dimethylphenoxy)ethyl-N-2-hydoxyethyl-N,N-dimethylammoniumiodide (5 g.) and syrupy phosphoric acid (90%; 12 g.) was heated at 100in vacuo for 8 hours, a current of air being drawn continuously throughthe mixture. Phosphorus pentoxide (6 g.) was then added and the mixtureheated in vacuo for a further 12 hours. The resulting viscous solutionwas mixed with water (200 ml.) and a boiling saturated solution ofbarium hydroxide added, with stirring, until the pH of the resultingsuspension reached about 8.5. After standing overnight at 0, theprecipitated barium phosphate was filtered 0E and 2 N-sulphuric acid wasadded slowly to the filtrate until no more precipitate formed. Theresulting barium sulphate was filtered oil and the filtrate evaporatedin vacuo. The crystalline residue was treated with boiling acetone,filtered off and dried in vacuo. It was then dissolved in methanol (50ml.) and the resulting solution was percolated through a column ofAmberlite (LR. 45, OH- form), the column being finally washed with freshmethanol until a test spot of the eluate on filter paper showed noabsorption in U.V. light. The crystalline residue obtained fromevaporation of the combined washings was recrystallised from a mixtureof ethanol and propan-Z-ol 1:1) to give N-2-(4-benzoyl-2,6-dimethylphenoxy)ethyl N,N dimethyl- N 2'phosphatoethylammonium betaine monohydrate, melting point 206-207".

Example 7 N-2(2 bromo 4 methoxyphenoxy) ethylN-2'-hydroxyethyl N,Ndimethylammonium bromide was converted toN-2-(2-bromo-4-methoxyphenoxy)ethyl-N,N- dimethyl N 2phosphatoethylammonium betaine trihydrate, melting point 4951, bymethods analogous to those described in Example 6.

Example 8 N-Z-hydroxyethyl-N-methyl 1',2',3,4' tetrahydroisoquinoliniumbromide was converted to N-methyl-N-2-phosphatoethyl-1,2',3',4-tetrahydroisoquinolinium betaine, melting point237-238, by methods analogous to those described in Example 6.

Example 9 Tablets (0.555 g.) of N-Z-(2-bromo-4-methoxyphenoxy)ethyl-N,N-dimethyl-N-Z-phosphatoethyl ammonium betaine were made bymixing the ester (0.25 g.) in a fine powder with lactose (0.25 g.) andstarch (0.05 g.) granulating the mixture with alcohol or alcoholicpolyvinyl pyrrolidino or a mixture of equal parts of alcohol and Water,drying the granules at 40, adding magnesium stearate (0.005 g.) as alubricant and compressing the mixture.

Example 10 Tablets (0.505 g.) of N-2-(2 bromo-4-rnethoxyphenoxy)ethyl-N,N-dimethylN-2-phosphatoethyl ammonium 6 betaine were made bygranulating the ester (0.5 g.) in a fine powder with equal parts ofalcohol and water. Magnesium stearate (0.005 g.) as a lubricant wasadded, and the mixture compressed directly.

Example 11 Injection solutions containingN-2-(2-bromo-4-methoxyphenoxyethyl)-N,N-dimethyl-N-2-phosphatoethylammonium betaine in water of injection (0.2 g. per ml.) were made byautoclaving the solution at 15 lb. steam pressure for 30 minutes in unitdose ampoules or multidose containers. For the latter, the water forinjection contained benzyl alcohol (1.0%), phenol (0.5%) or chlorocresol(0.1%).

Example 12 Tablets and injection solutions containingN-o-chlorobenzyl-N,N-dimethyl N 2 phosphatoethylammonium betaine orN-o-chlorobenzyl-N-methyl-N-di-(2-phosphatoethyl)ammonium betaine weremade by methods analogous to those described in Examples 9, 10 and 11.

Example 13 N,N-di-(Z-hydroxyethyl)-N-methylamine (1.2 g.) was added to asolution of o-fluorobenzyl bromide (2.1 g.) in acetone (3 m1.), when aspontaneous reaction ensued. After standing for 15 minutes, theresulting mixture was heated to reflux for 1 hour. The resultingN-o-fiuorobenzyl N,N di (2 hydroxyethyl) N methylammonium bromide wasfiltered 0E and recrystallised from propan- 2-ol, melting point 99-100.

Example 14 N,I*-l-di-(2-hydroxyethyl)-N-methylamine was reacted witho-nitrobenzyl bromide by methods analogous to those described in Example13. The resulting N,N-di- (2 hydroxyethyl)-N-methylN-onitrobenzylammonium bromide was recrystallised from methanol, meltingpoint 153154.

Example 1 5 A solution of 1-cyclohexyl-1-phenyl-3-(1-pyrrolidinyl)-propan-l-ol (2.9 g.) and 1-bromo-2-hydroxyethane (1.9 g.) in acetone (15ml.) was boiled under reflux for 24 hours. The reaction mixture wascooled and filtered to giveN-(3-cyclohexyl-3-hydroxy-3-phenyl-propyl)-N-(Z-hydroxyethyl)pyrrolidinium bromide, melting point 168169.

Example 16 o-Chlorobenzhydrol (44 g.) was reacted with hydrogen chloridein benzene, and the resulting o-chlorobenzhydrylchloride reacted withanhydrous piperazine (70 g.) in toluene (375 ml.) at 70-80" for 12hours. The solution was washed with water until the washings wereneutral, and extracted with dilute hydrochloric acid (5%).N-o-chlorobenzhydryl piperazine was liberated from the acid extracts,taken into ether, dried over potassium carbonate, and distilled at 1.3mm., boiling point 140-142".

N-o-chlorobenzhydryl piperazine (7.1 g.) was dissolved in acetonitrile(25 ml.). 2-bromoethanol (3.7 g.) and anhydrous N,N,N-triethylamine (1 5ml.) were added to the solution. The reaction mixture was refluxed for10 hours, cooled, and diluted with anhydrous ether (250 ml.). Theprecipitated triethylamine hydrobromide was filtered off, and thefiltrate concentrated in vacuo on a steam-bath. The residual oil wasdissolved in ether, washed three times with water, and dried overpotassium carbonate. Ethereal hydrogen chloride was added in ex cess tothe dried ethereal solution to give N-o-chlorobenzhydryl-N' 2hydroxyethyl piperazine dihydrochloride, melting point 255.

The piperazine base was liberated from this dihydrochloride (8 g.), anddissolved in benzene. The solution ml.) was dried over potassiumcarbonate, and acetone (50 ml.) and methyl iodide (4.5 g.) added succes-7 sively. The solution was allowed to stand for 24 hours, and theprecipitated N-o-chlorobenzhydryl-N-methyl-N- 2-hydroxyethylpiperaziniumiodide collected; it had a melting point of 213214. It was dissolved inacetone (200 ml), and anhydrous ether (100 ml.) was added; theprecipitated pure iodide had a melting point of 215- 216.

Example 17 A mixture of N,N,N',N'-tetramethylhexamethylenediamine (1.7g.), o-2-bromoethyl-0,0-diphenylphosphate (8.0 g.) and anhydrous sodiumcarbonate (5.0 g.) in ethanol (25 ml.) was boiled under a refluxcondenser for '16 hours. The reaction mixture was filtered, and thefiltrate evaporated. The residual gum was shaken with a mixture of water(50 ml.) and ether (50 mL). A hot concentrated aqueous solution ofbarium hydroxide g.) was added to the aqueous extract, and the solutionboiled in a nitrogen atmosphere under a reflux condenser for 24 hours.The reaction mixture was filtered and the White solid washed with hotwater to give the dibarium salt of N,N di (2 phosphatoethyl)N,N,N',-N'tetramethylhexamethylenediammonium dibetaine, melting point greater than300.

We claim:

1. A therapeutically acceptable phosphate ester of a quaternary ammoniumcompound which contains a benzylammonium cation having the formulawherein X is selected from the class consisting of hydrogen, chlorine,bromine, methyl and nitro, and a pharmaceutica-lly acceptable non-toxiccarrier.

2. A therapeutically acceptable N-o-bromobenzyl-N,N-dimethyl-N-2-phosphatoethylammonium betaine.

3. A therapeutically acceptable N-o-chlorobenzyl-N-methyl-N,-N-di-(2-phosphatoethyllammonium betaine.

4. A therapeutically acceptable N-o-ch'lorobenzyl-N,-N-dimethyl-N-Z-phosphatoethylammonium betaine.

5. A process for the treatment of hypertension which comprises theadministration of a therapeutically acceptable phosphate ester of acompound twhose cation has the formula References Cited in the file ofthis patent UNITED STATES PATENTS 2,622,083 Velluz Dec. 16, 19522,725,394- Zenftman Nov. 29, 1955 2,890,984 Sahgun June 16, 19592,910,403 Brendel Oct. 27, 1959 2,916,510 Garner Dec. 8, 1959 2,953,591Garner Sept. 20, 1960 OTHER REFERENCES Myers et al.: I. of Org. Chem.,vol. 22, No. 2, February 1957, p. 180.

Merck Index, 7th ed., 1960, p. 812. (Copy in POSL.)

1. A THERAPEUTICALLY ACCEPTABLE PHOSPHATE ESTER OF A QUATERNARY AMMONIUMCOMPOUND WHICH CONTAINS A BENZYLAMMONIUM CATION HAVING THE FORMULA